1. Field of the Invention
The invention relates to an insert for holding an optical system, in particular a focusing optics, in a laser machining head, and a laser machining head which comprises such an insert.
2. Description of the Background
In the machining of a workpiece by means of a laser machining head, in particular in laser cutting, it is usual to provide a laser machining head with a housing into which an insert with a focusing optics is inserted, a laser beam running through the laser machining head to a cutting nozzle being focused by an optical system held in the insert such that a workpiece can be machined. The insert with the optical system for focusing the laser beam is designed here such that the optical system can be adjusted relative to the insert, on the one hand the optical system being capable of adjustment in a plane perpendicular to the laser beam, and on the other hand an adjusting device being provided which can be used to set the optical system in the longitudinal direction of the laser beam.
Thus, DE 295 07 189 U1 discloses a terminal head for machining a workpiece by means of a laser beam, which has a housing and an insert, which can be introduced laterally into the housing and has a focusing optics. An adjusting ring can be rotated from outside through a cutout in a front plate of the insert, in order to displace the focusing optics upwards or downwards. When the adjusting ring is being rotated, a horizontal flange is corotated. The horizontal flange has an internal thread which engages with an external thread of an adjusting cylinder. The focusing optics is mounted in the adjusting cylinder. The adjusting cylinder is supported in a rotationally secure fashion by means of a longitudinal slot in the laser beam direction, and can be displaced in an axial direction along the laser beam. When the adjusting ring is being rotated, it takes the adjusting cylinder correspondingly with it via the horizontal flange, and this leads to an axial displacement of the lens holder as a result of the engagement of the threads. Depending on the sense of rotation of the adjusting ring, the lens holder, and with it the focusing optics, are displaced upwards or downwards.
DE 38 14 985 A1 describes a further laser machining tool. Here, a lens is supported in a lens holder such that it can be displaced relative to a nozzle both in an axial and in a radial direction. To this end, the lens holder is pressed from below with the aid of a spring against a sliding frame which can be axially adjusted inside the outer wall with the aid of an adjusting nut. Setscrews in the sliding frame are actuated for the radial adjustment.
Thus, in the case of the known laser machining heads, a focusing optics is adjusted in the longitudinal direction of the laser beam by transforming a rotary movement into an axial movement according to the spindle principle. This conversion of a rotating movement into an axial movement results in a frictional contact between the lens holder provided with an external thread, and the adjusting ring provided with an internal thread, it being possible for this to result in abrasion leading to soiling of the focusing optics. Moreover, to promote sliding contact use is made as a rule of lubricants which can likewise contribute to soiling of the focusing optics.
During operation of the laser machining head, the heating of the focusing optics gives rise to a focal position displacement in the longitudinal direction of the laser beam. This focal position displacement in the laser beam direction must be manually corrected in the case of the known laser machining heads, which means that the operation of the laser machining head has to be interrupted.